Apparatus for cooling the crank webs of crankshafts during inductive hardening

ABSTRACT

When inductively heating crankshaft workpieces, there is a tendency for the crank webs to become locally overheated during heating of crankpin portions of the rotating crankshaft workpieces. This is overcome by the invention by the provision of a cooling arm which is pivoted in the manner of a pendulum, and which is biased for motion towards the crankpin during rotation of the crankshaft, whereby the webs are effectively cooled during the portion of revolution of the workpiece when they tend to become overheated.

United States Patent Inventor Gerhard Preyer Wermelskirchen, Germany Appl. No. 767,184

Filed Oct. 14, 1968 Patented June 1, I971 Assignee Deutsche Edelstahlwerke Aktiengesellschat't Kreield, Germany Priority Dec. 23, 1967 Germany APPARATUS FOR COOLING THE CRANK WEBS OF CRANKSHAFIS DURING INDUCTIVE HARDENING 4 Claims, 2 Drawing Figs.

US. Cl 266/6, 266/4 Int. Cl C21d 1/62 Field of Search 266/6 S, 4

PrimaryExaminen-James M. Meister Att0meyCushman, Darby & Cushman ABSTRACT: When inductively heating crankshaft workpieces, there is a tendency for the crank webs to become locally overheated during heating of crankpin portions of the rotating crankshaft workpieces. This is overcome by the invention by the provision of a cooling arm which is pivoted in the manner of a pendulum, and which is biased for motion towards the crankpin during rotation of the crankshaft, whereby the webs are effectively cooled during the portion of revolution of the workpiece when they tend to become overheated.

PMENTEUM H97! SHEET 1. BF 2 Inventor.- 37 69:11: r-d r-e cal-582,056

PATENTED JUN I ISTI SHEET 2 BF 2 Inventor: 'd r' 3 MMwuM APPARATUS FOR COOLING THE CRANK WEBS OF CRANKSHAF TS DURING lNDUCTlVE HARDENING This invention relates to the inductive hardening of the crankpins of crankshafts for internal combustion engines and particularly relates to apparatus for use in the so-called rotary method of inductively heating crankshafts, the said rotary method being one in which an inductor forming a closed heating loop on one side of a crankpin is placed into yielding contact with the surface thereof, and electric power is then applied at a constant rate to the inductor whilst the crankshaft is rotated at constant speed about the axis of symmetry of the mainshaft bearing of the crankpin.

Providedthat only the bearing surface of the crankpin is required to be inductively heated and hardened by subsequent quenching, difiiculties do not usually arise, however when the fillets and the adjoining retaining surfaces of the webs as well as the bearing surfaces are to be hardened, the maintenance of a constant speed of rotation and of a constant supply of electrical power does not result in the production of a uniformly heated layer in the surfaces to be hardened unless precautions are taken. This is due to the fact that the crankpins of crankshafts are situate between crank webs offset a considerable distance from the axis of symmetry of the crankshaft, the crank webs often having a large mass. lf electrical power is induced in the crankpins at a constant rate the heat generated in the work flows along the surface of the crankpin facing the axis of symmetry of the crankshaft, i.e. the inside-facing surface, into the webs of the cranks. Moreover heat flow is considerably impeded in the small remaining portions of the webs which surround the outside surfaces of the crankpins.

lf therefore the power supplied is based on the requirements of the insidefacing surfaces of the crankpins, considerable local overheating occurs and stress cracks may result after hardening. If however the supply of electrical power is based on the requirements of the outside-facing surfaces of the crankpins, i.e. the surfaces facing away from the axis of symmetry of the crankshaft, this may lead to the inside-facing surfaces thereof being insufficiently hardened.

In order to achieve a satisfactory inductive hardening effect according to the invention the supplyof electrical heating energy is based on the heat requirements of the inside surface of the crankpin workpiece, and to prevent overheating of fillet portions and retaining faces on the outside of the workpiece cooling is effected, which may be effected by conventional cooling techniques.

While cooling of the crank webs should be effective, it must also be achieved by the simplest possible mechanical means, and it is therefore the object of the invention to provide a solution of this problem by the provision of suitable control means. I

The required contacting pressure ie. biased movement, may be generated in conventional manner by springs, hydraulic or pneumatic means or with the aid of simple lever linkages.

The invention provides in inductive heating apparatus for inductively heating crankshafts of the type comprising means of rotating a crankshaft workpiece along a longitudinal axis thereof and an inductor for heating a crankpin of the said crankshaft workpiece; cooling means for cooling the crank webs in the region of the crankpins during rotation of the crankshaft workpiece, the said cooling means comprising a pendulum cooling arm, a plurality of sprayer heads mounted on said pendulum cooling arm, and control means for positively controlling the movement of the said pendulum cooling arm in response to movement of the crank webs of the rotating crankshaft workpiece.

According to a particular feature of the invention, this is achieved by attaching to the cooling arm a cord which runs over pulleys and which at its free end carries a weight.

An embodiment of the invention is hereinafter described and illustrated in the accompanying drawings, of which FlG. l is a side elevational view of apparatus according to the invention, and

FIG. 2 is a plan view of the apparatus of FIG. 1. Referring to FIG. 1, a crankshaft has a crankpin l and a web 2. The crankpin is exposed to the effect of an inductor 4 and the entire crankshaft is assumed torotate about an axis in the direction indicated by arrow 3.

The inductor element 4 is attached to transformer carriage 5. Likewise attached to the said transformer carriage is a rail 6 which at its upper end carries pulleys 7 and 8. Hingeably attached in the manner ofa pendulum to the bottom end of the rail 6 is a pendulum-cooling arm 9 composed of tubular elements and, as indicated in FIG. 2, provided with sprayer heads 10 facing the edges of the webs. The cooling liquid to the said sprayer heads is supplied through the hinge of the pendulum cooling arm. The upper end of the cooling arm carries a strut ll to which a cord 12 is attached. The said cord is taken over pulleys 7 and 8 and its freely depending end carries a weight 12. By this arrangement the pull of the weighted rope biases the cooling arm 9 for movement towards the web, spacing members l4 maintaining the arm a. given distance away from the web surface.

FIG. 1 indicates the two extreme positions reached by the crank web, the left hand position being shown in full lines and the righthand position in discontinuous lines. The cooling arm participates in this motion and in FIG. 1 the extreme positions of the cooling arm corresponding to the positions of the web are likewise shown in continuous and discontinuous lines.

The sprayer head may continue to operate during the entire rotary motion of the crankshaft. However, cooling will be effective only when the cooling arm is in the position indicated in FIG. 1 in full lines, because only in this position will those parts of the crank webs that are exposed to the risk of overheating be within range of the sprayer heads. in the other extreme position of the crank webs parts of the workpiece are exposed to the liquid spray which are remote from the inductively heated parts of the workpiece.

Whatl claim is:

1. ln inductive heating apparatus for inductively heating crankshafts of the type comprising means for rotating a crankshaft workpiece along a longitudinal axis thereof and an inductor for heating a crankpin of the said crankshaft workpiece; cooling means for cooling the crank webs in the region of the crankpins during rotation of the crankshaft workpiece, the said cooling means comprising a pendulum cooling arm, a plurality of sprayer heads mounted on said pendulum cooling arm, and control means for positively controlling the movement of the said pendulum cooling arm in response to movement of the crank webs of the rotating crankshaft workpiece.

2. Apparatus according to claim 1, in which control means are provided for positively controlling the motion of the said pendulum cooling arm in response to the motion of crank webs during rotation of the crankshaft workpiece about the longitudinal axis of the crankpin undergoing heating.

3. Apparatus according to claim 1, in which the said control means comprises a cord attached to the said pendulum cooling arm extending over a pulley system, and a weight attached to the free end of the said cord, whereby the said pendulum cooling arm is biased for movement towards the crankpin undergoing heating.

4. Apparatus as in claim 3 wherein said control means further includes spacing means for maintaining said pendulum cooling arm a given distance away from the web surface. 

1. In inductive heating apparatus for inductively heating crankshafts of the type comprising means for rotating a crankshaft workpiece along a longitudinal axis thereof and an inductor for heating a crankpin of the said crankshaft workpiece; cooling means for cooling the crank webs in the region of the crankpins during rotation of the crankshaft workpiece, the said cooling means comprising a pendulum cooling arm, a plurality of sprayer heads mounted on said pendulum cooling arm, and control means for positively controlling the movement of the said pendulum cooling arm in response to movement of the crank webs of the rotating crankshaft workpiece.
 2. Apparatus according to claim 1, in which control means are provided for positively controlling the motion of the said pendulum cooling arm in Response to the motion of crank webs during rotation of the crankshaft workpiece about the longitudinal axis of the crankpin undergoing heating.
 3. Apparatus according to claim 1, in which the said control means comprises a cord attached to the said pendulum cooling arm extending over a pulley system, and a weight attached to the free end of the said cord, whereby the said pendulum cooling arm is biased for movement towards the crankpin undergoing heating.
 4. Apparatus as in claim 3 wherein said control means further includes spacing means for maintaining said pendulum cooling arm a given distance away from the web surface. 